Warm- or cold-season grasses make up the majority of lawns. Cold-season grasses grow well in colder regions and vice versa. Lawns consist of thousands of individual grass plants that obtain the majority of their nutrients from the soil. Over time, the soil loses its food supply for the grass. Lawn fertilizer enhances the soil, which in turn feeds the grass plants. Improper fertilization causes plants to wilt or die because there is not a balance of nutrients. Growers who learn how to pick a lawn fertilizer correctly increase their chances of having a healthy, vibrant lawn.
Lift a section of sod measuring approximately 1 square inch. Wet the soil with water, then test it with a soil pH test kit (test strips provide better results when used with wet soil). Write the results on a piece of paper as a reminder. Replace the section of sod.
Measure the square footage of the lawn with a tape measure. Write this down on the same paper as the pH results. Lawn fertilizer application instructions require knowing the lawn's square footage.
Examine the grass and determine what type is growing in the lawn. Read the back of a grass seed package's back to determine the nutrients required for that particular type of grass. If the grass type is unknown, follow the growing recommendations for your specific growing region.
Examine the lawn for weeds and pests. Lawns full of weeds, such as dandelions and clover, benefit from fertilizers with weed herbicides. Lawns with grubs or other pests benefit from fertilizers with pesticides. If both problems exist, use a fertilizer that has both.
Determine which nutrients are lowest in the soil pH results and pick a lawn fertilizer accordingly. The first number in a lawn fertilizer's number type refers to its nitrogen levels. The second is phosphorus, and the final number is potassium. Lawns two or more years old benefit from a lawn fertilizer where the first number of the three is highest, such as 20-10-10 lawn fertilizer. Lawns that are older and damaged from winter benefit from the first and last numbers being equal, such as 20-10-20.
Pick a granular time-released lawn fertilizer if you're in a geographical region that receives frequent rain. Rainfall dissolves fertilizer slowly, for continual soil benefit. Pick a liquid lawn fertilizer for dry geographic regions. Soak the lawn prior to application to prevent root or leaf burn.